Vapor-supplying cartridge



July 20, 1948. g, ABEL 2,445,706

VAPOR-SUPPLYING CARTRIDGE Filed June 1, 1944 ig.1. ,9 l ,2 Fig.2. Fi .3.

ITWGWTOT'I WMiam P Zabel,

His A't't'owr'nexd.

Patented July 20, 1948 VAPOR-SUPPLYING GARTRIDGE 'William P. Zabel, Cleveland Heights, Ohio, as-

Signor to General'Electric Company,

ration of New York Application .June 1, 1944, Serial No. 538,262

1 Claim.

activated. The liberation of such matter may take place after the initial evacuation of the discharge envelope, and matter thus disseminated in the envelope may also serve the purpose of a getter to clean up residual gas or vapor and improve the vacuum. The invention is here described in detail as applied to the manufacture of a simple type of photocell having a cathode surfaced with an antimony and caesium combination; but it will be understood that it is applicable to other types of discharge devices, such as elec- I tron multipliers, for example, as well as to other types of phototube besides those here illustrated. Likewise, it is applicable to electrodes surfaced with other combinations besides antimony and caesium, such as bismuth and caesium, antimony and rubidium, or any useful combinations of vaporizablefirst group metal with metal of the fifth group, of the periodic system.

The invention relates particularly to novel cartridges or capsules charged with material for supplying the matter to be'liberated in the dis charge device envelope, such as caesium or other vaporizable first group or alkali metal, and to the manufacture and charging of such cartridges, whichinray be made of thin walled metal tubingseamless, welded, or of sheet metal strip with edges butted, lapped or crimped-together without welding or bracing. Various features and ad vantages of the invention will become apparent from the description of species and iorms of embodiment, and from the drawings.

In the drawings, Fig. 1 shows a vertical longitudinal section through a photocell device having my novel cartridge in its appendix or exhaust tubeyand Figs. 2 and'3 are diagrammatic sectiona1 views of ovens for processing photocellswith my cartridge.

'Fig. 4 .is an oblique side View of the cartridge; Figs. 5 and Bare end views of the cartridge, showing difterentforms of end closure; Fig. '7 is a tilted view of a pellet for charging or loading the cartridge; and Figs. Sand 9 are-end views showing different forms of reduced vent opening.

:A photocell device X'is shown in Fig. 1 as comprising a short glass envelope tube Ill having its sule 2'0 and its charge zoo-0.4)

ends sealed by fusion to the margins of abutting annularly embossed discs or electrode headers II, I2 of sheet metal (such as chrome -iron),generally similar to those used f or the ends of the tubular incandescent lamps which are commercially known as Lumiline lamps. The cathode header I l which appears at the bottom in Fig. 1 carries a coaxial sheet 'metalcathode disc is (as of Nichrorne or nickel) welded thereto and shown with its outer edge turned up toward the anode header I2. As shown, a glass appendix orexhaust tube I5 is attached or sealed by fusion to the outer side of the centrally apertured header II, substantially coaxial with its aperture and with a corresponding central opening IS in the disc IS. The anode header I2 which appears at the top in Fig. 1 is not apertured, but carries a central sheet metal part I8 (as of nickel foil) that presents a substantially flat surface toward'the cathode I3. Current connections l9, I5 are shownwelded to the headers I I, I2.

In the manufacture of the photocell device above described, the cathode disc I3 is welded to the header II, and the tube ID is sealed at one end to this header, the cathode disc I3 is surfaced with a thin coating of antimony thermally deposited thereon, the metal part I8 is welded to the header I2, and the header is sealed to the end of the tube ill, the glass tube l5 being also sealed to the header I I As shown in Fig. 1, the metal cartridge or capsule 20 of my invention, containing a caesiumyielding charge 2 I, is placed in the tube I5 somewhat below the cell X. To assure that theca-psule '20 shall remain in the desired position in the tube I5, a fixed support ma be provided for it, such as a stiff helical (nickel) wire coil spring 22 bent crooked and then inserted in the tubeI'S to the position desired, where it is held by-its resilient pressure and friction against thetube walls, without obstructing the passage through the tube.

In processing a cell X with the cartridge 20 in the tube I5 as above described, the device may first be baked and exhausted in an'oven (not shown), as in the old process, being thus brought to a temperature of the order of 300 to 340C; The device having come hot'out of this exhaust oven, jet(s) of cooling air from one or more nozzles 23 may be blown on the tube I5 to cool it, especially around and above the capsule 20; and while the tube I5 is being thus cooled, the cap- 2I may be heated by highfrequency induction, by means of a coil 24 placed close to the tube "I5 opposite the upper end of the capsule 20, thus flashing the charge 2| and depositing condensed caesium in the tube I above the capsule 20, as indicated by stippling at 25, without its entering the cell X to any material extent, and without heating the tube It sufficiently to risk cracking it. The tube I5 may then be sealed or tipped off long at 25 as shown in Fig. 2. The caesium being thus in the tube l5 at some distance below the photocell X, the cathode I3 may then be activated by driving a suflicient amount of caesium from the tube I5 up into the cell X, to react with the antimony In preparation for this, the cell X may be placed in an oven R as shown in sealed-off tube l5 extending oven bottom-and heated to temperature, of the order of C., thus bringing the antimony temperature at which caesium with it, and also driving any have entered the cell X when flashed down into the tube I5, which remains at room temperature (e. g., 20 (3.). The tube 5 may then be heated to vaporize the caesium at 25 and drive it up through the tube I5 and the opening I6 (see Fig. 1) into the cell X, where it deposits on the hot antimony surface down through the a suitably elevated some 220 to 260 surface at l3 to a enough to provide a slight surplus of caesium in cell X.

After the tube l5 has been heated in the oven S for the required length of time, the oven S may be removed, to let the tube I 5 cool off slightly, whereupon the photocell X may be removed from the oven R and sealed or tipped off from the tube |5 so close that the tip does not project beyond the shelter of the recess in the header I I as indicated in heavy dotted lines at 21 in Fig. 1. After tipping off, the cells X are baked in an oven (not shown) at a temperature of the order of 180 C.

for some 20 minutes, which brings the excess of clean up residual gas, and causes its absorption by internal surfaces of the cell structure. It also tends to stabilize the cells against changes in sensitivity during storage.

I 'he processing of a photocell as just described corresponds to what is disclosed in the application of Clifton G. Found, Serial No. 520,052, filed January 28, 1944, now Patent 2,413,442, issued Decartridge and its use.

As shown in Figs. 1, 4, 5, and 6, the cartridge or capsule 20 consists of a short length of thinwalled seamless sheet metal tubing (as of nickel so thin that it may fairly be termed foil) that contains the charge 2| and has its ends more or less closed at 28, 29 to retain the charge, The tube blanks may preferably be annealed in hydrogen at a temperature of the order of 1100 C. for 10 minutes, to soften and clean them. The charge 2| may consist of material which yields metallic caesium vapor under heat, such as a in Figs. 1, 4, and 5, the lower end 28 of the tube 20 that rests on the spring 22 is mashed and crimped completely shut in a V-section, though if desired this crimping might be of semicircular or U-section as in Fig, 6. Instead of being in the form of powder, the charge 2| is pelleted into one or more pellets 30 of circular or cylindrical outline somewhat smaller than the bore of the tube 20. While a single pellet or slug 0f sufiicient axial dimension would answer, it is more convenient to employ thin, flat disc-like pellets 30 such as shown in Fig. 7, since this allows of readily varying the total charge 2| by merely varying the number of pellets used. It is desirable, however, in any case, that the charge 2| should occupy substantially less than the whole internal length of the cartridge 20 between its end closures As shown in Figs. 1 and 4, the upper end 29 of the tube 20 that is directed toward the cell X is not quite closed, but is formed to a narrow vent opening, too narrow to pass either the p l ts 0 or their cindered residues after flashing. As shown in Figs. 4 and 8, this tube end 29 is reduced by mashing and crimping to form a multiplicity of radially arranged narrow hollow fins or flutes so that the deformed tube section may be termed stellar or cruciform, depending on the number of such hollow fins, three being shown in Fig. 8. While the width and area of vent opening afforded by the hollow fins 3| can generally be made as small as desirable without approaching the practical limit of such deformation of the tube 20, extreme reduction of vent opening can be attained by flattening the fins so that their sides touch, leaving only very small openings at their ends and at their common center, as illustrated in Fig. 9, which shows four such nearly closed-up fins 3|.

and hence cannot interfere with inserting the cartridge in the tube l5, as might be the case if this tube end 29 were merely flattened. The like is also true of the angular or semicircular crimp- 28 as shown in Figs. 5 and 6. But the stellar or cruciform type of vent opening 3| has an advantage over a V or U-shaped vent opening in that it is symmetrical and so assures a more uniform distribution of the upward blown metal vapor in the tube l5 and opening with any lateral outlet(s) aimed directly at the cell inlet it, so that the vapor enters the cell without being deflected or losing its force. It will also be apparent from Fig. 4 that the ends of the cartridge have distinctly different shapes so as to readily distinguish which end is to exhaust tube |5.

The compression required to form the alkalimetal-yielding material of the charge 2| into cohesive pellets 30 reduces its bulk very considerably as compared with the same material in powder form, so that the cartridge 20 can be made shorter than would otherwise be advantageous. The empty space in the cartridge tube 20 above the charge 2| that is shown in Figs. 1 and 4 is not without importance, however, for

5 cordingly, the cartridge 20 flashes gently and with-out any fusion of the metal tube wall. The Vapor escapes through the vent opening 3| without danger of rupturing the tube 20 or cracking the tube l5; indeed, the discharged cartridge shows no change in form whatever. The expanded cinders formed. by the flashing of the pellets 30 remain in the cartridge, and any cinder fragments are caught in the narrow opening 3|, so that dirty cells X with brown spots of cinder on their cathodes l3 are avoided.

Shrinkage in manufacture is reduced because of the improved and uniform performance of the cartridges 2!] when flashed, the quality and uniformity of the cells X is improved, and the material and manufacturing costs of the cartridges 20 themselves are very low.

The method of manufacturing the cartridge described above is claimed separately in my divisional application Serial No. 713,347, filed November 30, 1946.

What I claim as n w and desire to secure by Letters Patent of the United States is:

A cartridge for supplying vapor when heated comprising a length of sheet metal tubing having one end thereof firmly mashed shut to a nonlinear contour of substantially no greater lateral extent than the diameter of the tubing, the other end of said tubing being crimped into radially arranged narrow hollow fins defining a, narrow multifluted vent opening which is likewise of REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,072,987 Porter Sept. 9, 1913 1,415,075 VVilber May 9, 1922 1,424,180 Pritchard Aug. 1, 1922 1,687,496 Henkel Oct, 16, 1928 1,688,245 Muir Oct. 16, 1928 1,718,899 Fischer June 25, 1929 1,895,867 Sinden Jan. 31, 1933 2,054,030 Charlton Sept. 8, 1936 2,082,268 Varian June 1, 1937 2,093,273 Haslauer Sept. 14, 1937 2,094,675 Salzberg Oct. 5, 1937 2,100,746 Miller Nov. 30, 1937 2,339,064 Dreyer Jan. 11, 1944 

